Help with Deed of Assignment

My husband has an Endowment with his ex. They split up shortly after buying a house 24 years ago. The house was sold and the mortgage paid off, but he continued to pay into an endowment. It has been running for 24 years, and he has been paying roughly £40 a month, On maturity the Policy will be worth just shy of £16k so the return will only be the same as a saving plan.
The real issue is, when he and his ex split, they went on their separate ways and he lost contact with her.
He has been trying in vain (not been able to trace her for the entire period due to her moving away) to get the Deed of Assignment signed over to him as sole ownership.
He has recently managed to make contact, and has offered her a sum to sign over to him, she has refused and has since been ignoring calls/messages etc.
We have been for a free 30 min session to see a Solicitor and they think the outcome is very much in her favour.
If she ignores his requests, then she will be liable for half of the policy on maturity, where a cheque will be issues to each party in both of their names. Given they no longer have a joint account, this money can not be cashed by either- so virtually worthless.
She has not paid one penny into the policy. And he has bank records to show this. If she choses to, she can just ignore his requests and on maturity, then nobody will benefit.
Is there anything that can be done, short of taking it court? and if that is the only option, how much would this realistically cost? and moreover what is the likelihood of it being successful in his favour?